Powershell Remoting and Single Threaded Apartments (STA)

I've recently been testing a Powershell module I developed to see if it worked as expected via Powershell Remoting.

The module must run in Single Threaded Apartment mode (STA) because of a dependency on the MSBuild engine. Normally, when running locally you would need to launch Powershell with the -STA switch. However you cannot specify this switch when using remoting since Powershell is started and hosted by WSMan/WinRM (wsmprovhost.exe)

In this case the Powershell startup configuration is managed via the following family of cmdlets:

Set-PSSessionConfiguration

New-PSSessionConfiguration

You can also explore the session configuration in the WSMAN namespace:

cd WSMan::localhost\Plugin

   WSManConfig: Microsoft.WSMan.Management\WSMan::localhost\Plugin

Name                      Type                 Keys

----                      ----                 ----

Event Forwarding Plugin   Container            {Name=Event Forwarding Plugin}

microsoft.powershell      Container            {Name=microsoft.powershell}

Microsoft.PowerShell32    Container            {Name=Microsoft.PowerShell32}

microsoft.ServerManager   Container            {Name=microsoft.ServerManager}

SEL Plugin                Container            {Name=SEL Plugin}

WMI Provider              Container            {Name=WMI Provider}

The default configuration for a Remoting Session is 'microsoft.powershell', which will start Powershell in MTA.

To start a remote powershell session in STA mode you need to set the following InitializationParameters in the configuration.

pssessionthreadapartmentstate = STA

pssessionthreadoptions = UseNewThread

To test my module created a new PSSessionConfiguration, which also specified a StartupScript to automatically perform the import, and then specified the configuration when starting the remoting session:

New-PSSession -Computername SERVER1 -ConfigurationName TESTCONFIG

Incidentally, the configuration is persisted as an XML stream in the following registry location:

HKLM\Software\Microsoft\Windows\CurrentVersion\WSMAN\Plugin